I've had a P0336 (CKP sensor performance) code ever since I put the 427 in my car 2 years ago. I've replaced the sensor twice with the same results. Last weekend I went through the entire GN service manual troubleshooting guide with no smoking guns found. Anyone have any ideas what else could be causing this? The clearance between the sensor and reluctor ring is the same as the stock LS6 was (still have it sitting in a crate). The resistance between the CKP sensor connector and PCM connector was all good (0 ohms). I routed the wires as shown in the service manual (away from EMI sources). A visual inspection of the reluctor ring (using a boro scope) revealed no apparent damage.

The car runs well. The problems a fluctuating tachometer (about 3-400 rpm) and my data logs abviously show random 3-400 rpm fluctuations. And due to the p0336 code, I can't do the sensor relearn procedure (which sets the p1336 code). I'mm afraid I'm leaving a lot of ponies on the table due to fluctuating timing caused by this (does it affect actual timing).

A post in the C4 section mentions that a lope in the idle may cause this code (which I don't understand if that applies to the C5), but as listed in my sig, my car is VERY modified and this may be a cause (although there isn't a huge lope to the idle).

Any experts have any thoughts?? I'm looking to try anything at this point.

Derrick

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2001 Corvette Z06, C5R 427, PTS Twin T-64 turbo system, AFR 225's, FAST 90mm intake/TB, 95# injectors, Comp cams 238/242, Callies crank, Oliver rods, Mahle pistons, Roadrunner PCM, and some other 'odds-n-ends'
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2007 Big Dog K-9 Chopper, the "HEAD TURNER"

 

Shim the CKPS with a paperclip and snug down lightly. Try it again. See if fixes it. If it does. Create a permanent shim for the CKPS.

 

I thought maybe the clearance between the reluctor and sensor could be too far already and be causing this, and was considering shaving the sensor mount to get it closer, but never thought I may need to move it further away. There are no signs of contact between the reluctor and sensor as it is. Does it make sense to move the sensor tip further away from the reluctor wheel?

Derrick

 

I've had a few GM vehicles in my shop that have had a similar problem like this. Some have drivability porblems some did not. Shiming the CKP fixed the problem everytime. But through all of the car/trucks not a single one has had contect between the reluctor wheel and the CKPS. Try shimming it first and if that does not fix anything you can move on to something else.

 

Well, I tried shimming the CKP sensor with the same results. So I bit the bullet and pulled the motor to find the reluctor ring bent. Unfortunately, the pictures I took are too large to upload. I think this was shipping damage when I got the crank and I never thought anything about it at the time. I've bent the ring back into shape and will be putting the motor back together as soon as some new main bearing arrive (crank end play at .010", just slightly loose). I hope this fixes the problem and I will actually see how this motor truly performs. Still shooting for over 1000 RWHP.

Derrick

 

Just got around to doing the CKP relearn today. Also drove the car for the first time today. WAYYYY smoother running. It's nice having a steady tach vice oscillating 400 RPM around the actual RPM.... Some things that I had problems with before and now don't that may be related to the P0336 are :

Tach smoothness
Running rough
Part throttle surging
Car now reeturns to a rock steady idle after revving it (vice hunting)
It no longer "hangs up" at 1200 RPM when the throttle cracker is activated (now returns to idle RPM when clutch is pushed and car moving)

The only downside, which I just need time to tune out, is that it's very "lopey" at idle and cold. It settles out as it warms up. I'll try playing with the timing at idle over the next few days to try and solve this problem (not really a problem, but gives away some of the stealth the car has otherwise).

Derrick

 

Glad you found the problem. I had several thousand dollars in damage to my car, also a 427. Seems that the Futral Cam people had ground the cam "reluctor ring", for lack of better terms, .040" undersize compared to "normal", which GM service manuals, and no one else, I might add, can give me an answer to as to what the "normal", or "service limit" size is. Code kept showing PO336, but when W2W up here got far enough into it, and isolated the cam sensor from the crank sensor, it cam up as the cam sensor every time! According to the good folks at Howell Engine Development, the two sensors are tied together on the circuit board ONLY, NOT the wiring harness!! And somehow, the PO336 "beat" the code for the cam sensor out to the "check engine" light!!!! After W2W had isolated what was actually happening (The car ran GREAT for 30,000 miles!), and after much careful scrutiny by yours truly, I discovered this manufacturing defect (The cam ring being WAY undersize). It has had my car off the road for almost 2 years now, and nearly exploded in fire, causing thousands more in "heat damage, though it never actually burst into flames. How hot? Though the coolant never got above 180 degrees, the exhaust system got RED HOT!!!I have NO rubber left on my exhaust hanger straps, and not a trace of melted rubber, either!!! It must have vaporized! We (W2W and I) theorize that it ran well for the first 30,000 miles until the cam bearings got worn just enough and allowed the cam to move away from the sensor just ever so slightly, maybe .002"-.003". It still ran O.K. until all that aluminum in the block heated up and expanded the sensor (Up above on the LS1's) even further away. What a nightmare. Glad you didn't have an experience like this....And hope no one else does, either.